Observation of the Ξ−b→J/ψΛK−decay

The observation of the decay Ξ−b→J/ψΛK−is reported, using a data sample corresponding to an integrated luminosity of 3 fb−1, collected by the LHCb detector in ppcollisions at centre-of-mass energies of 7and 8 TeV. The production rate of Ξ−bbaryons detected in the decay Ξ−b→J/ψΛK−is measured relative to that of Λ0bbaryons using the decay Λ0b→J/ψΛ. Integrated over the b-baryon transverse momentum pT<25 GeV/cand rapidity 2.0 <y <4.5, the measured ratio is fΞ − b fΛ0 b B(Ξ − b → J/ψΛK− ) B(Λ0 b → J/ψΛ) = (4.19±0.29 (stat)± 0.15 (syst))×10−2, where fΞ−band fΛ0bare the fragmentation fractions of b →Ξ−band b →Λ0btransitions, and Brepresents the branching fraction of the corresponding b-baryon decay. The mass difference between Ξ−band Λ0bbaryons is measured to be M(Ξ − b )− M(Λ0 b ) = 177.08±0.47 (stat)± 0.16 (syst)MeV/c2.S

Measurement of the J/ψ pair production cross-section in pp collisions at √s=13 TeV

The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of √s=13 TeV, corresponding to an integrated luminosity of 279 ±11 pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.S

Measurements of prompt charm production cross-sections in pp collisions at √s=5 TeV

Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5 TeV. The data sample corresponds to an integrated luminosity of 8.60 ± 0.33 pb−1 collected by the LHCb experiment. The production cross-sections of D 0, D +, D +s, and D ∗+ mesons are measured in bins of charm meson transverse momentum, p T, and rapidity, y. They cover the rapidity range 2.0 < y < 4.5 and transverse momentum ranges 0 < p T < 10 GeV/c for D 0 and D + and 1 < p T < 10 GeV/c for D +s and D ∗+ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1 < p T < 8 GeV/c are determined to be σ(pp→D0X)=1004±3±54μb,σ(pp→D+X)=402±2±30μb,σ(pp→D+sX)=170±4±16μb,σ(pp→D∗+X)=421±5±36μb, where the uncertainties are statistical and systematic, respectively.S

Study of prompt D0 meson production in pPb collisions at √sNN=5 TeV

Production of prompt D0 mesons is studied in proton-lead and lead-proton collisions recorded at the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of 1.58±0.02 nb−1 recorded at a nucleon-nucleon centre-of-mass energy of √sNN=5 TeV. Measurements of the differential cross-section, the forward-backward production ratio and the nuclear modification factor are reported using D 0 candidates with transverse momenta less than 10 GeV/c and rapidities in the ranges 1.5 < y ∗ < 4.0 and −5.0 < y ∗ < −2.5 in the nucleon-nucleon centre-of-mass system.S

Measurement of the B0s→J/ψη lifetime

Using a data set corresponding to an integrated luminosity of 3fb−1, collected by the LHCb experiment in ppcollisions at centre-of-mass energies of 7 and 8TeV, the effective lifetime in the B0s→J/ψηdecay mode, τeff, is measured to be τeff = 1.479±0.034 (stat)±0.011 (syst)ps. Assuming CPconservation, τeffcorresponds to the lifetime of the light B0smass eigenstate. This is the first measurement of the effective lifetime in this decay mode.S

Measurement of CP violation parameters and polarisation fractions in B0s→J/ψK∗0 decays

The first measurement of CP asymmetries in the decay B0s→J/ψK∗(892)0 and an updated measurement of its branching fraction and polarisation fractions are presented. The results are obtained using data corresponding to an integrated luminosity of 3.0 fb−1 of proton-proton collisions recorded with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. Together with constraints from B 0 → J/ψ ρ 0, the results are used to constrain additional contributions due to penguin diagrams in the CP -violating phase ϕ s , measured through B 0s decays to charmonium.S

Differential branching fraction and angular moments analysis of the decay B 0 → K +π− μ + μ − in the K∗0,2(1430)0 region

Measurements of the differential branching fraction and angular moments of the decay B 0 → K +π− μ + μ − in the K +π− invariant mass range 1330 < m(K +π−) < 1530 MeV/c 2 are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q 2, between 0.1 and 8.0 GeV2 /c 4. For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q 2 range 1.1-6.0 GeV2 /c 4.S

First study of the CP-violating phase and decay-width difference in B0s→ψ(2S)φ decays

A time-dependent angular analysis of B0s→ψ(2S)φdecays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb−1collected during Run1 of the LHC. The CP-violating phase and decay-width difference of the B0ssystem are measured to be φs=0.23+0.29−0.28±0.02 radand s=0.066+0.041−0.044±0.007 ps−1, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that φsand shave been measured in a decay containing the ψ(2S)resonance.S

Measurement of forward W → eν production in pp collisions at √s=8 TeV

A measurement of the cross-section for W → eν production in pp collisions is presented using data corresponding to an integrated luminosity of 2 fb−1 collected by the LHCb experiment at a centre-of-mass energy of √s=8 TeV. The electrons are required to have more than 20 GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive W production cross-sections, where the W decays to eν, are measured to be σW+→e+νe=1124.4±2.1±21.5±11.2±13.0pb, σW−→e−ν¯e=809.0±1.9±18.1±7.0±9.4pb, where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The W + /W − cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of W boson branching fractions is determined to be B(W→eν)/B(W→μν)=1.020±0.002±0.019, where the first uncertainty is statistical and the second is systematic.S

Measurement of forward J/ψ production cross-sections in pp collisions at √s=13 TeV

The production of J/ψ mesons in proton-proton collisions at a centre-of-mass energy of √s=13 TeV is studied with the LHCb detector. Cross-section measurements are performed as a function of the transverse momentum p T and the rapidity y of the J/ψ meson in the region p T < 14 GeV/c and 2.0 < y < 4.5, for both prompt J/ψ mesons and J/ψ mesons from b-hadron decays. The production cross-sections integrated over the kinematic coverage are 15.30 ± 0.03 ± 0.86 μb for prompt J/ψ and 2.34 ± 0.01 ± 0.13 μb for J/ψ from b-hadron decays, assuming zero polarization of the J/ψ meson. The first uncertainties are statistical and the second systematic. The cross-section reported for J/ψ mesons from b-hadron decays is used to extrapolate to a total bb cross-section. The ratios of the cross-sections with respect to √s=8 TeV are also determinedS